Today the crema makes up a substantial part of a coffee beverage. It binds a large part of the coffee aromas and thus substantially contributes to a good coffee flavour. Crema formation is influenced by various factors. For example by the quality of the brewed coffee and the type of brewing process.
From patent application EP 1 743 554 A1 a brewing device for a fully automatic coffee maker is known wherein a crema valve is connected with a brewing unit and a coffee outlet. The crema valve regulates the outflow of the coffee brewed in the brewing unit with a sealing plug and a compression spring. When the brewed coffee under high pressure is pressed through an opening on the sealing plug the coffee is swirled around and a very fine-pored froth is created which forms the crema. With this coffee maker the production of the crema can practically not be influenced by the user of the coffee maker. The coffee or the coffee beverage it contains in each case thus looks visually similar in each case.
With another known brewing device for coffee a mechanical throttling device is installed by means of which it is possible through mechanical adjustment of the throttling device to throttle the flow of the outflowing coffee at an end of the coffee outlet distant from the brewing chamber. Although this throttling has an influence on the quantity of crema produced, the influence is rather small however. Furthermore, the throttling has an influence on the coffee temperature and thus on the quality of the brewed coffee. There is furthermore the risk that the throttling device is clogged.